Among the most common fatal diseases are vascular diseases, in particular cardiac infarction. This is caused by disease of the coronary vessels (atherosclerosis). Deposits (atherosclerotic plaque) thereby cause a blockage of the coronary vessels. In particularly serious cases this can lead to total occlusion of the coronary vessels or chronic total coronary occlusion (CTO). In the past such occlusions could generally only be treated by means of a bypass operation. In recent years laser angioplasty (PTLA) has also become established as a method for removing plaque, particularly in the case of long stenoses (>2 cm) and total occlusion. However with PTLA there is a not insignificant risk of injury in the form of hemorrhage, damage or perforation/dissection of the vascular wall.
In February 2002 a new instrument—a so-called CTO catheter—was licensed by the FDA for the removal of chronic total occlusions. This device operates in a similar fashion to expansion tongs by applying pressure to break up the plaque in the coronary vessels bit by bit, thereby allowing gradual removal of the total vascular occlusion. Such a CTO catheter for removing a chronic total occlusion is for example disclosed in'U.S. Pat. No. 5,741,270 “Manual Actuator for a Catheter System for Treating a vascular occlusion” and in U.S. Pat. No. 6,120,516 “Method for Treating Vascular Occlusion” in particular FIG. 18. A known product is the Frontrunner CTO catheter from LuMend, Inc., Redwood City, Calif.
Intervention with the CTO catheter is carried out subject to X-ray control with an angiography system. The disadvantage of this method is that the coronary vessels are only displayed as two-dimensional and only the actual constriction is shown in the X-ray image. In order to show the vessel clearly, contrast agents also have to be injected into the coronary vessels. Some patients are known to be allergic to contrast agents and some patients report a sudden hot sensation. Also it is difficult for medical personnel to distinguish between plaque and vascular wall during the intervention. This increases the risk of the expansion tongs being deployed in the wrong place, resulting in injury to the vascular wall.
Insertion of an IVUS catheters (Intravascular Ultrasound) into the vessel improves the imaging information but has the disadvantage that a relatively expensive catheter also has to be inserted into the patient and must be removed from the vessel before insertion of the CTO catheter. An IVUS system is for example disclosed in EP 0 885 594 B1 and in U.S. Pat. No. 5,193,546.
Significantly better local resolution, particularly in the relevant close-up range, is provided by an OCT catheter (Optical Coherence Tomography), which is inserted separately into the vessel. The OCT method is for example disclosed in WO 01/11409 A2, in U.S. Pat. No. 5,921,926 and in EP 0 815 801 B1. This technique operates in a similar fashion to imaging ultrasound (B mode). The essential physical principle is based on the Michelson interferometer. The disadvantage of this method is that the OCT device has to be withdrawn from the vessel whenever the CTO catheter is inserted.